One vertex per element, one color per generator, with an edge from x to x·s.
(2,4)(5,6)(7,11)(8,10)(9,12)(13,14,17,21,18,22,26,28)(15,19,20,27,23,16,24,25)(5,7)(6,9)(8,12)(10,11)(15,23)(16,19)(20,24)(25,27) involution — undirected(1,2,3,4)(6,10)(9,11)(13,15)(14,19)(16,22)(17,20)(18,23)(21,27)(24,26)(25,28)(7,12)(9,11)(15,23)(16,19)(20,24)(25,27) involution — undirected(6,10)(9,11)(13,16,17,25,18,19,26,27)(14,20,21,23,22,24,28,15)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.